#!/usr/bin/env python
"""
procky.py - An SMTP Proxy
License: GPL 2; share and enjoy!
Author: Sean B. Palmer
Usage: ./procky.py

SMTP Specification: 
   http://www.ietf.org/rfc/rfc821.txt
Procky is to be found at: 
   http://inamidst.com/misc/procky.py
"""

import sys, os, socket, smtplib

bufsiz = 1024
smtpserver = os.environ.get('SMTP_SERVER')

class Proxy(object): 
   def __init__(self, sock): 
      self.sock = sock
      self.state = None

      self.sender = ''
      self.recipients = []
      self.exit = False

   def sendline(self, line): 
      print '<-', '%r' % line
      self.sock.send('%s\r\n' % line)

   def run(self): 
      domain, port = self.sock.getsockname()
      self.sendline('220 %s Service ready' % domain)

      while True: 
         input = self.sock.recv(bufsiz)
         if not input: break
         print '->', '%r' % input

         if self.state == 'DATA': 
            response = self.body(input)
            if response == 'QUIT': break
            continue

         command = input[:4].upper()
         # The following are RFC 821 4.5.1's minimum requirement
         commands = {'HELO': self.helo, 'MAIL': self.mail, 
                     'RCPT': self.rcpt, 'DATA': self.data, 
                     'RSET': self.rset, 'NOOP': self.noop, 
                     'QUIT': self.quit}
         if commands.has_key(command): 
            response = commands[command](input)
            if response == 'QUIT': break
         else: self.sendline('500 Syntax error, command unrecognized')

   def helo(self, input): 
      self.state = 'HELO'
      self.sendline('250 OK')

   def mail(self, input): 
      if self.state != 'HELO': 
         self.sendline('503 Bad sequence of commands')
         return

      self.state = 'MAIL'
      i, j = input.find('<'), input.rfind('>')
      self.sender = input[(i + 1):j]
      self.sendline('250 OK')

   def rcpt(self, input): 
      if self.state not in ('MAIL', 'RCPT'): 
         self.sendline('503 Bad sequence of commands')
         return

      self.state = 'RCPT'
      self.recipients.append(input)
      self.sendline('250 OK')

   def data(self, input): 
      if self.state != 'RCPT': 
         self.sendline('503 Bad sequence of commands')
         return

      self.state = 'DATA'
      self.mailbody = ''
      self.sendline('354 Start mail input; end with <CRLF>.<CRLF>')

   def body(self, input): 
      self.mailbody = self.mailbody + input

      if self.mailbody.endswith('\r\n.\r\n'): 
         self.mailbody = self.mailbody[:-5]
         sent = self.sendmail(self.mailbody)
         self.state = 'HELO'

         if not sent: 
            self.sendline('554 Transaction failed')
            self.sock.close()
            return 'QUIT'
         else: self.sendline('250 OK')

   def sendmail(self, input): 
      input = self.munge(input)

      for recipient in self.recipients: 
         i, j = recipient.find('<'), recipient.rfind('>')
         sendee = recipient[(i + 1):j]

         if sendee == 'py@sys.exit': 
            self.exit = True
            return True

         if not smtpserver: 
            print >> sys.stderr, 'E: No SMTP_SERVER specified!'
            self.recipients = []
            return False

         sent = True
         try: 
            smtp = smtplib.SMTP(smtpserver)
            smtp.set_debuglevel(0)
            smtp.helo(smtpserver)
            smtp.sendmail(self.sender, sendee, input)
            smtp.quit()
            break
         except Exception, e: 
            print >> sys.stderr, 'E:', e
            continue
         else: sent = False

      self.recipients = []
      return sent

   def munge(self, input): 
      return input

   def rset(self, input): 
      self.mailbody = ''
      self.state = 'INIT'
      self.sendline('250 OK')

   def noop(self, input): 
      self.sendline('250 OK')

   def quit(self, input): 
      self.sock.close()
      if self.exit: sys.exit(0)
      return 'QUIT'

def runproxy(conn): 
   p = Proxy(conn)
   p.run()

def main(): 
   sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
   sock.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)
   sock.bind((socket.gethostname(), 25))
   sock.listen(5) # 5 is usually the maximum

   while True: 
      conn, address = sock.accept()
      runproxy(conn)

if __name__=="__main__": 
   main()